1. Field of the Invention
Hypodermic needles are commonly used to both inject substances into and extract substances out of human and animal bodies. Such hypodermic needles are typically disposable and are discarded after one use. The problem presented by the disposal of a hypodermic needle, and indeed, any handling of the hypodermic needle after its use, is the potential for being injured by the sharp end of the needle. This is particularly dangerous because following the perforation of a patient's skin, the needle may be contaminated and therefore capable of spreading diseases, such as hepatitis and AIDS.
2. Description of Related Art
A number of devices have been described that provide for some form of protective shield about the tip of a hypodermic needle, see, for example, the following:
Bastien, U.S. Pat. No. 2,571,653 PA1 Adams, U.S. Pat. No. 2,847,995 PA1 Armao, U.S. Pat. No. 3,134,380 PA1 Bloch, U.S. Pat. No. 3,354,881 PA1 Alvarez, U.S. Pat. No. 4,139,009 PA1 Wickham, U.S. Pat. No. 4,237,882 PA1 Kling, U.S. Pat. No. 4,373,526 and PA1 Larson, U.S. Pat. No. 4,639,249
The disadvantage inherent in the above devices is that none provide positive protection. In each case, a used hypodermic needle could conceivably still perforate a subsequent handler's skin. While the devices described by McFarlane in U.S. Pat. No. 4,500,312 and 4,573,981 do provide positive protection once in place, considerable risk of perforation is presented in replacing the sheath. The devices described by Leeson et al., U.S. Pat. No. 3,890,971; Sampson, U.S. Pat. No. 4,573,976 and Mitchell, U.S. Pat. No. 4,631,057, are affixed to a syringe and, subsequent to an injection, can be extended beyond the exposed needle and locked into position. The disadvantage inherent in these designs is that a non-automatic deliberate movement is required to slide the guard in place. This leaves the needle tip exposed for a period of time. Furthermore, the needle tip is merely retracted and not actually encapsulated, and finally, these devices envelope the entire syringe and are therefore of considerable size and cost. Such a configuration precludes such a design's use in conjunction with a multi-draw blood drawing device. Recently ICU Medical, Inc. introduced a product called "High Risk Needle," which has a similar disadvantage in that a deliberate movement is required after its use leaving the needle tip exposed for a period of time.